An event-based model for continuous media data on heterogeneous disk servers |
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Authors: | K Selçuk Candan E Hwang VS Subrahmanian |
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Affiliation: | (1) Department of Computer Science and Engineering, Arizona State University, Box 875406, Tempe, AZ 85287-5406, USA; e-mail: candan@asu.edu , US;(2) Department of Computer Science, University of Maryland, College Park, MD 20742, USA; e-mail: hwang@cs.umd.edu , US;(3) Department of Computer Science, University of Maryland, College Park, MD 20742, USA; e-mail: vs@cs.umd.edu , US |
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Abstract: | Over the last few years, there has been intense work on the problem of retrieval of continuous media (CM) data from disk.
However, no single unified framework exists within which such retrieval problems can be studied. In this paper, we first propose
a formal model for CM data retrieval from heterogeneous disk servers. This model can be used to characterize CM data retrieval problems
independently of how data is laid out on disk, and what objectives (e.g., minimize client delay, maximize buffer utilization, etc.) the
system manager is interested in. We then show how using this formal model, we can neatly define what it means to optimally
handle events that occur in movie-on-demand (MOD) systems. Examples of such events include new clients entering the system,
old clients leaving the system, continuing clients doing pause, rewind and fast-forward operations. Multiple events may occur
simultaneously and we show how such events trigger state transitions in the system. We then develop an algorithm called the
QuickSOL algorithm that handles events occurring in MOD systems. This algorithm works in two phases: in the first phase, it quickly
finds a way of handling as many of the events occurring at time t as possible. In the second phase, it optimizes the solution found in the first phase. The advantage is that the algorithm
can be interrupted anytime after the first phase is completed. We report on experiments showing that QuickSOL works well in practice. |
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